Glow switch and method of manufacture thereof



y 13, 1954 N. c. BEESE 2,678,979

GLOW SWITCH AND METHOD OF MANUFACTURE THEREOF Filed April 10, 1952 INVENTOR /V. C". 55535 if I 6% U l ATTORNEY Patented May 18, 1954 UNITED sTA'rss rew-"r OFFICE GIIOW SWITCH ANDMETHOD OF 'MANUFACTURE THEREOF Norman C..Becse, Verona, N. 'J., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application April '10, 1952, Serial No. 281,513

4 Claims. 1 My invention relates to glow switches 'for use with fluorescent lamps and, more particularly,

:to the gas used therein and to the method or switch manufacture.

provide a fill gas for use me glow switch.

A further'object of my invention is to provide an economical method of manufacturing uniform glow switches.

The above objects and other objects which will become apparent as the description proceeds are achieved by using a gas within the lamp which consists of 0.4% to 5% hydrogen and the balance substantially argon.

The descrpition of my invention will'be better understood by reference to the accompanying drawing in which the sole figure illustrates a glow switch having a gasfill according to myinvention.

I have found that an economical uniform glow switch may be produced if the switch contains a gas comprised of argon with approximately 0.4% to 5% hydrogen. The preferred portion of hydrogen 1.5% by volume. The argon which is used may be tank argon having approximately 0.15% of nitrogen therein. The above percentages refer to the gas within the glow switch after the manufacturing steps are completed and after the switch has been seasoned. Seasoning may be accomplished by operating the switch for a short period of time.

The glow switch is comprised of an envelope I 2 having sealed into one end thereof a mount I4. The mount It is closed by a press I6 at the interior end thereof. Supported by the press l6 and passing therethrough is a lead-in conductor and contact electrode l8 and a lead-in conductor and support 9 for a bimetallic electrode 26. The bimetallic electrode 25 is mounted on the leadin conductor 19 close to the contact electrode 18. The lead-in conductor and contact electrode 18 and the lead-in conductor l9 extend exteriorly of the lamp to provide leectric terminals 22 to make electrical connection to the glow switch. The envelope is filled at a pressure between approximately 25 and 35 mm. of mercury with an inductive ballast.

'2 .an ionizable gas 24 which will support a glow discharge between the contact electrode 1-8 and the bimetallic electrode 20.

As is familiar to those acquainted with the art, glow switches are used to start fluorescent lamps. The glow switch is connected in series with the filamentary electrodes of a fluorescent lamp and When voltage is applied to the circuit, a glow discharge is established between the contact electrode !8 and the bimetallic electrode 20. When the bimetallic electrode 20 is heated sufficiently by the glow discharge to engage the contact electrode 18 the glow dis charge is short-circuited and a larger current flows through the series circuit heating thefilamentary electrodes connected in series with the glow switch. The bimetallic electrode 29 begins to cool once the glow discharge is short-circuited. When the bimetallic electrode it cools and pulls away from the contact electrode [8, the circuit is broken and a high voltage surge occurs across the lamp electrodes due to the large inductance of the ballast. The quicker the circuit is broken by the bimetallic electrode the larger the voltage surge and the more satisfactory the operation of the glow switch in starting the lamp. When the bimetallic elecetrode cools, an arc is drawn between it and the contact electrode. This arc lowers the voltage surge.

If the glow switch contains a gas which consists of argon with approximately 0.4% to 5% of hydrogen by volume of the total mixture, the arc, which occurs on the disengagement of the contact electrode and the bimetallic electrode 20, will be quenched very rapidly and a high voltage surge will result. Rapid quenching reduces the power loss in the switch itself and permits a greater portion of the energy stored in the inductive ballast to be applied to the starting of the lamp. This produces higher eiiective starting voltage extending over longer time intervals. If more than 5% hydrogen is present the switch will not function properly in starting the lamp.

In manufacturing, it has been found necessary to use a fill gas having between 1.5% and 6% hydrogen by volume, with a pressure within the lamp of from about 25 mm. to 35 mm. of mercury. The optimum fill gas appears to be one which has approximately 4.2% hydrogen therein. A higher percentage of hydrogen must be added to the fill gas than required in the final switch in order to make up for losses of hydrogen which occur during the manufacture and initial operation of the glow switch. These losses apparently are due to the high difiusion rate ing water vapor introduced therein in the form of water or by the use of hygroscopic or deliquescent salts with a getter to absorb the 02 produced.

In manufacturing the glow switch the mount including the stem and the two electrodes is first sealed into the envelope I2. Heretofore, it has been necessary to cool the mount and the envelope after sealing and prior to the introduction of the fill gas. However, with my fill gas the switch may be exhausted while hot immediately fter sealing the mount therein and then filled with the gas of my invention. The exhausting and filling connection is then tipped oii as is well known in the art.

Switches made according to my invention will give a life of approximately 60 hours on a continual switching test. The switches of the prior art have been considered good switches if they last 2o hours on the continual switching test which comprises applying line voltage to the switches connected in series with a fluorescent lamp inductive ballast and allowing them to go through their heating and cooling cycle continuously for a period of hours. The switches with the argon-hydrogen mixture have a life up to three times that of the switches of the prior art. Also the shrinkage during manufacture is considerably reduced by the method of manufacture as outlined above.

t will be seen from the above that switches made with the fill gas of my invention are uni form, have a long life, and are economical to manufacture.

I claim:

1. A. glow switch for the star ing of fluorescent lamps comprising an enclosing envelope having an ionizable medium therein. at a pressure between about mm. and mm., and a pair of electrodes disposed in said envelope beglow discharge, said medium being comprised of about 0.4 to 5 per cent hydrogen by volume and the balance substantially of argon.

2. A glow switch for the starting of fluorescent lamps comprising an enclosing envelope having an ionizable medium therein at a pressure between about 25 mm. and 35 mm., and a pair of electrodes disposed in said envelope between which a glow discharge occurs during operation of said glow switch, one of said electrodes being a bimetallic element heated by the glow discharge and deflectable into engagement with the other of said electrodes to extinguish the glow discharge, said medium being comprised of about 1.5 per cent hydrogen by volume and the balance substantially of argon.

3. The method of manufacturing a glow switch for use with a fluorescent lamp comprising, seal.- ing the mount of said switch into one end of the switch envelope, exhausting the envelope of the switch while it is still warm from sealing, and filling said envelope with a fill gas having about 1.5 to 6 per cent hydrogen by volume and the balance consisting substantially of argon to a pressure between. about 25 mm. and 35 mm.

4. The method of manufacturing a glow switch for use with a fluorescent lamp comprising, sealing the mount of said switch into one end of the switch envelope, exhausting the envelope of the switch while it is still warm from sealing, and

filling said envelope with a fill gas having about 4.2 per cent hydrogen by volume and the balance consisting substantially of argon to a pressure between about 25 mm. and 35 mm.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,895,855 Lockwood c Jan. 31, 1933 2,133,492 Vatter Oct. 18, 1938 2,228,210 Hays Jan. 7, 1941 2,236,671 Chirelstein Apr. 1, 1941 2,336,923 Carpenter Dec. 14, 1943 

